# Water pipes change sound when hot water arrives. Why? **URL:** \ **Category:** Factual Questions\ **Created:** [July 6, 2004, 12:34am UTC](https://boards.straightdope.com/t/water-pipes-change-sound-when-hot-water-arrives-why/253720 "2004-07-06T00:34:15Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![CuriousD](https://avatars.discourse-cdn.com/v4/letter/c/c4cdca/32.png) [@CuriousD](https://boards.straightdope.com/u/CuriousD)\ **Post date:** [July 6, 2004, 12:34am UTC](https://boards.straightdope.com/t/water-pipes-change-sound-when-hot-water-arrives-why/253720/1 "2004-07-06T00:34:15Z")
Could someone explain why the sound of water pipes changes with the incoming water`s temperature ??? It`s not like there`s a change of friction going on… 😕 ---
**Author:** ![hlanelee](https://avatars.discourse-cdn.com/v4/letter/h/3bc359/32.png) [@hlanelee](https://boards.straightdope.com/u/hlanelee)\ **Post date:** [July 6, 2004, 1:02am UTC](https://boards.straightdope.com/t/water-pipes-change-sound-when-hot-water-arrives-why/253720/2 "2004-07-06T01:02:39Z")
The hot water causes the pipes to expand. The new size makes them sound different. ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [July 6, 2004, 1:58am UTC](https://boards.straightdope.com/t/water-pipes-change-sound-when-hot-water-arrives-why/253720/3 "2004-07-06T01:58:37Z")
The same question answered. > **[Different sound of hot water in pipes](https://boards.straightdope.com/sdmb/showthread.php?t=189284)** > > This is a strange question and probably has a pretty simple answer, but I can’t figure it out and it’s bugging me. The hot water in our house takes a good 60 seconds or so to warm up completely when you turn on the hot water tap. Therefore, whenever... ---
**Author:** ![PaulFitzroy](https://avatars.discourse-cdn.com/v4/letter/p/2acd7d/32.png) [@PaulFitzroy](https://boards.straightdope.com/u/PaulFitzroy)\ **Post date:** [July 6, 2004, 2:44am UTC](https://boards.straightdope.com/t/water-pipes-change-sound-when-hot-water-arrives-why/253720/4 "2004-07-06T02:44:36Z")
I never put hot water in my water pipe. ---
**Author:** ![Popup](https://avatars.discourse-cdn.com/v4/letter/p/94ad74/32.png) [@Popup](https://boards.straightdope.com/u/Popup)\ **Post date:** [July 6, 2004, 12:11pm UTC](https://boards.straightdope.com/t/water-pipes-change-sound-when-hot-water-arrives-why/253720/5 "2004-07-06T12:11:44Z")
> [@antechinus](#): > > The same question answered. > > [http://boards.straightdope.com/sdmb/showthread.php?t=189284](http://boards.straightdope.com/sdmb/showthread.php?t=189284) Actually, it never got a decent answer. I still believe that the viscosity has a large impact on the pitch of the sound, but I haven’t been able to prove it. Maybe a question for the Master? ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [July 6, 2004, 12:19pm UTC](https://boards.straightdope.com/t/water-pipes-change-sound-when-hot-water-arrives-why/253720/6 "2004-07-06T12:19:59Z")
Yeah it got answered - viscosity is not a factor. ---
**Author:** ![Popup](https://avatars.discourse-cdn.com/v4/letter/p/94ad74/32.png) [@Popup](https://boards.straightdope.com/u/Popup)\ **Post date:** [July 6, 2004, 2:08pm UTC](https://boards.straightdope.com/t/water-pipes-change-sound-when-hot-water-arrives-why/253720/7 "2004-07-06T14:08:47Z")
> [@antechinus](#): > > Yeah it got answered - viscosity is not a factor. It’s pretty clear that the viscosity is not a factor for the _propagation_ of sound. I _believe_, however, that the sound arises when uneven edges and depositions along the surfaces cause eddy currents and turbulence in the flow, and to me it’s equally obvious that this would depend on the viscosity of the liquid. One reason I’m arguing so strongly in favour for the viscosity is that it’s the parameter that changes the most over the temperature spectrum we’re looking at. ([cite](http://www.engineeringtoolbox.com/24_596.html)) But if you can come up with a more plausible explanation for the origin of the noise, I’m all ears.